The present invention relates to a refrigeration compressor having an oil filter. In particular, the present invention is directed to the placement of the oil filter within the body of the compressor.
A refrigeration compressor is an integral part of a refrigeration unit, along with an evaporator, expansion valve, and condenser. A compressor compresses the refrigerant, thus raising its temperature. This compressed refrigerant gas then enters the condenser and is condensed into liquid form by contacting it with another cooler medium, such as ambient air, ground water, or water from a cooling tower loop. After the heat is removed from the refrigerant in the condenser, the condensed refrigerant liquid goes to an expansion valve. The expansion valve allows a limited quantity of liquid refrigerant to enter the evaporator, while maintaining the pressure difference between the condenser (at higher pressure) and the evaporator (at lower pressure). The liquid refrigerant entering the evaporator evaporates after contacting a heat load, such as the refrigerator interior or ventilation air that is to be cooled, thus absorbing heat from the heat load. The refrigerant vapor leaves the evaporator and returns to the compressor to repeat the cycle.
A refrigeration compressor commonly has a cast metal housing and a need for lubrication of the moving parts, such as the gears and bearings. A refrigeration compressor contains an oil sump where lubricating oil collects and a lubrication system to direct oil from the sump to each lubrication point. The oil lubrication system has an oil filter for removing particulate matter from lubrication oil.
The oil filter associated with a refrigeration compressor has been provided in a separate pressure vessel attached onto the outside of the compressor, or even contained in a separate pressure vessel unattached to the compressor body.
Having a separate pressure vessel increases the potential for oil leaks. In addition, an oil filter attached to the housing of a compressor is not easily replaced. In many refrigeration compressors in the prior art it is quite difficult to replace the oil filter without losing the charge of refrigerant. Another problem with prior art refrigeration compressors and their separate oil filters is that the oil filter element itself gets contaminated quite easily, and this greatly reduces its filtering efficiency. External oil filters also make it more difficult for clean, filtered oil to reach the lubrication points, since the oil has to travel farther (and thus pick up more impurities) to get to its targets. In addition, an oil filter vessel projecting from the compressor is exposed and subject to injury, particularly when the compressor is being shipped and installed.
U.S. Pat. No. 5,159,820 discloses an oil separator integrally mounted on a compressor. In this patent, elements that separate the refrigerant from the oil and then filter the oil are attached to the compressor casting and operatively connected to the compressor. This reference, however, does not disclose an oil filter located inside of the compressor casting.